A plasma process is an indispensable technique for manufacturing semiconductor devices. In recent years, further miniaturization of semiconductor devices constituting LSI has been required to meet a demand for high-integration and high-speed of LSI.
However, for a capacitively coupled plasma processing device or an inductivity coupled plasma processing device, an electron temperature of generated plasmas is high, and a region in which a plasma density is high is also limited. For this reason, it is difficult to realize plasma processing according to the requirement of further miniaturization of semiconductor devices.
Therefore, the realization of such miniaturization requires generating plasma with a low electron temperature and a high plasma density. In order to meet this requirement, there is proposed a device for performing a plasma process on a semiconductor wafer (hereinafter, referred to as a “wafer”) by generating a surface wave plasma inside a processing vessel using a microwave (see Patent Document 1).
In Patent Document 1, there is proposed a plasma processing device which generates a surface wave plasma having a high plasma density at a low electron temperature by transmitting a microwave through a coaxial tube to radiate the same into a processing vessel and exciting a plasma generation gas using an electric field energy of a surface wave of the microwave.
However, the plasma processing device of Patent Document 1 has a structure in which, in order to irradiate the processing vessel with the microwave through the coaxial tube, a ceiling portion of the processing vessel is configured such that a quartz dielectric plate is inserted between the surface wave plasma and an antenna, and a processing gas is supplied into the processing vessel through a sidewall of the processing vessel. In this way, since the gas is supplied from a portion other than the ceiling portion, the flow of the gas cannot be controlled. As such, a good control of the plasma cannot be achieved.
To address this, in Patent Document 2, there is proposed a technique which installs a shower plate made of a dielectric material, the shower plate having a plurality of gas discharge holes formed in a bottom surface of an antenna, and introduces a processing gas into a processing vessel along a path directed vertically downward from the shower plate. This arrangement forms a vertical gas stream inside the processing vessel and uniformly supplies the processing gas, thereby forming uniform plasma.